Industry sources say ANA has indicated to suppliers that its RFP will be issued in the coming weeks, possibly before the end of June.

The RFP will call for proposals from Airbus for the A380 and from Boeing for the 747-8. The sources speculate that it will probably be for between five and 10 aircraft. The sources also say ANA may ask for proposals for the Airbus A350 XWB as well as for additional 777s.

Airbus and Boeing have been waiting for years for the RFP. Airbus has yet to sell the A380 or the A350 to any airline in Japan, a market in which Boeing has a dominant share. Boeing in turn will be fighting particularly hard to make its first 747-8 sales in Japan and not lose market share to its rival.

ANA had long said it did not see a role for ultra-large aircraft in its fleet, but earlier this year revealed that it will be looking in the near future for large widebodies to replace its remaining 747-400s from 2012. It has already been replacing 747-400s with 777-300ERs.

Asiana has been in discussions with Airbus and Boeing on an order for A350s and/or 787s for some time.

Industry sources say it has now taken an internal decision to place a major order for A350s on purchase arrangements, as well as take 787s on lease arrangements.

The sources caution that formal agreements have yet to be finalised, but if they are firmed up they are likely to be announced in the coming weeks, possibly at the Farnborough air show in July.

Asiana chief executive Chan Bup Park declined to comment in an interview at the International Air Transport Association annual general meeting in Istanbul, except to say that "hopefully in the middle of June" a decision can be taken.

Asiana has at the same time been assessing the Airbus A380 and 747-8, but Park says there is "a little more to go" in the evaluations. Industry sources say a decision on large aircraft is now more likely in the second half of the year.